Can 2phones be linked to the same AirTag?

Yes, as long as both phones are signed into the same Apple ID.

From: How to reset your AirTag - Apple Support

"An AirTag can be associated with one Apple ID.

However, if yu are asking about multiple users, read about upcoming features in iOS 17 (not yet released); go to this web site: iOS 17 Preview - Apple

"Find My.

Share AirTag or Find My network accessories with up to five other people. Everyone in the group can use Precision Finding and play a sound to pinpoint the location of a shared AirTag when they’re nearby."

Only 1 AppleID can be linked to any AirTag.

However, there are changes coming in iOS17 which you can read about here:

iOS 17 makes iPhone more personal and intuitive - Apple